Automatic safety mechanism for mechanically operated cutting knives severing strip materials



P 1952 J. NASMITH' AUTOMATIC SAFETY MECHANISM FOR MECHANICALLY OPERATED CUTTING KNIVES SEVERING STRIP MATERIALS 3 Sheets-Sheet 1' Filed May 18, 1948 l 2 J. I. NASMITH 2,591,592

AUTOMATIC SAFETY MECHANISMFOR MECHANICAL-LY OPERATED CUTTING KNIVES SEVERING STRIP MATERIALS Filed May 18, 1948 3 Sheets-Sheet 2 H f 12 7 ii ea l INVENTOR JOHN 1. NASIH AGENTS 2,591,592 TED April 1, 1952 J. NASMITH AUTOMATIC SAFETY MECHANISM FOR MECHANICALLY OPERA CUTTING KNIVES SEVERING STRIP MATERIALS 3 Sheets-Shet 5 Filed ma 18, 1948 mv'swroa JO N I. NAS ITH AGENTS Patented Apr. 1, 1952 AUTOMATIC SAFETY MECHANISM FOR MECHANICALLY OPERATED CUTTING KNIVES SEVERING STRIP MATERIALS John Irving Nasmith, London, England, assignor to Vickers-Armstrongs Limited, London, England, a British company Application May 18, 1943, Serial No. 27,810 In Great Britain May 20, 1947 Claims.

It is a common requirement to be able to cut off automatically lengths of strip material supplied from a reel, whilst the strips are being applied to work pieces in motion, usually in rotary motion. By way of example the work pieces can be cartons or cardboard boxes to be covered with an ornamental or protective layer of adhesively coated paper or the like.

For such a process the operator is required to bring the cut end as left by the automatic cut off and place it in position on the work piece, which is then set in motion, usually by a foot pedal provided on the machine, and controlled by the operator, and the strip guided and controlled by the operator is applied on to the work, the correct length of strip being then automatically cut off independently of the operators attention.

Normally, the operators fingers are in no danger, but there exists no means of preventing the pedal control being actuated and the knives performing a cutting stroke whilst the operators fingers are in the knife closure; and accidents due-to inattention, or cleaning or other manipulation, are liable to occur. Access to the knife region is inherent to the operation of the machine, and the object of the present invention is to provide full safety short of deliberate action.

According to the present invention means is provided whereby in order for the pedal or other operators control alone to cause the cut-off to function, the strip material must pass through the knife closure under tension and in a particular region relative to the knife closure.

In carrying the invention into practice, the cut-ofi mechanism takes the normal form of a pair of cross cutting knives, one blade being substantially stationary relatively to the framing and transversely disposed in relation to the strip material to be severed. The other knife is pivotally mounted and mechanically operated, e. g. through the medium of a known cam and spring mechanism, to open and close the knife as required to allow the passage of the strip and in conjunction with the fixed knife, cut it off at the proper time to give the required cut length. Except as described later, the driving of this operating mechanism is under the control of the operator, e. g. by the usual foot pedal operated clutch, the clutch also serving by suitable connections to revolve the work holder supporting the blank to which the strip is being applied. This well-known construction is left unaltered, and need not be particularised further, the safety arrangements which are the subject of the present invention being superposed thereon. It need only be mentioned further that in order to cut off the moving strip satisfactorily without danger of tearing, the strip must be, at the moment of cut off, in close proximity to the fixed knife. This condition must be, and is attained by an initial relative adjustment of the cut off mechanism and the work in support.

In order that the invention may be clearly understood and readily carried into effect drawings are appended hereto illustrating somewhat diagrammatically an embodiment thereof, and wherein:

Figure 1 is a broken side elevation of the relevant part of the machine frame,

Figure 2 is a plan view of Figure 1,

Figures 3, 4, 5 and 6 show in sectional side elevation respectively the following conditions of the cut-off mechanism: firstly, the displaceable driven knife under spring actuation about to sever the strip, secondly, the said knife returned under cam control and the tension in the strip being reestablished, thirdly, the said knife at the furthest point of cam control with no tension in the strip, and finally the said knife locked against actuation.

Referring to the drawings, the relevant part of the machine frame is indicated in Figures 1 and 2 by the reference numeral [4, the knife I being actuated by a cam l5 through a cam rod l6 loaded by a spring I3 and connected to one corner of an oscillating striker plate I! of substantially rhomboidal form, this plate loosely pivoting on one of a pair of trunnions 2' of a knife frame embodying two side arms 2 and a cross-bar 2A on which the knife I is mounted so as to'be disposed transversely to the strip 3 to be severed, the frame l4 having bearings 4 at either end for the trunnions. The striker plate I1 is formed between its pivotal support and its'rear edge with a stop H which abuts against one of the side arms 2 of the knife frame to impel the knife forwardly and upwardly. Additionally, however, immovably secured to one of the trunnions 2' and revolving with the frame 2 is an interference stop member 5 which functions as described later. On an axis parallel to that carrying the pivoted cut-off blade frame, and relatively suitably disposed thereto is provided a second pivoted frame 6 carried by tr-unnions l in end bearings, and forming part of the safety control. The cam rod I6 is slotted as at [6 to slide over one of these trunnions; The frame 6,. takes the form of two pivoted side arms Ba and 6b, connected at their ends, some distance away from their pivot centre, by two rods 8 and 9, an upper and a lower respectively, between which the strip 3 is passed, and falling just short of the fixed cutting blade It] so as to pass by the cutting edge of this when the cut takes place. This frame 6 is light, freely mounted and partially counterpoised as at 6. Immovably secured to the axis of this frame is a second interference stop member H.

The pivoted frame it is normally free to take up any position between required working limits, its temporary position at any time being determined by the position of the tensioned strip material 3 being pulled over a guide roller I2 from the supply reel between the knife closure at that time. If there is no tension in the strip 3 (e. g. after severing) this frame falls to its lowest limiting position under gravity (see Figures 5 and 6).

The two interference stops 5 and H are so relatively shaped, disposed and arranged, that the actuated cut-off knife l cannot be operated by its control spring l3 (see Figure l) to perform the out, unless the strip tension actuated frame 6 has been raised by the strip 3 into the position shown in Figure 4 in close proximity to the level of the fixed cut-off knife Ill. Only if this condition is satisfied can the cut-off knife I "operate to perform the cut, the strip material being freed from the weight of the frame 6 immediately before the shearing operation by the cross bar 2a engaging against and slightly lifting the frame 6. Under all other circumstances, the actuated cut-off knife I cannot move in the direction required to sever the strip, due to the interference stops 5 and H co-o'perating to prevent this motion as shown in Figures 5 and '6. s

The action of this mechanism relative to the operator is therefore as follows: When no operation is in progress, the strip 3 is not under tension and consequently the cut-off is prevented from functioning if the operators control is operated accidentally or for any specific purpose, such as may be required in setting up for instance The same applies if an incomplete operation is interrupted for any reason, up to a point immediately preceding cut-off, due to inertia effects releasing the tension. Normally, i. e. during continuous operation of the machine, tension in the strip 3 is continuous and the operators hands are fully occupied manipulating the work. The time interval separating the safe and unsafe position of the mechanism is so short as to be practically instantaneous, and the transference of the fingers to the knife closure from a working position is impossible in practical operation.

The only way the fingers can be caught in the knife closure is by deliberately sustaining the strip tension, presenting the hand to the knife closure, and operating the control pedal. This must be a deliberate triple action and cannot occur accidentally.

The invention thus provides complete protection'to the operator.

I claim:

1. In a machine for feeding strip material to work pieces a fixed shearing member with its cutting edge disposed transversely relative to the direction of feed of the strip material through the machine, a co-operating movable shearing member, means supporting the latter shearing member for movement relatively to the other for severing the strip material in lengths, freely suspended guiding means for'the strip material, and an abutment connected to said guiding means and so related positionally, relatively to the means supporting the movable shearing member, as to engage said supporting means and act as a stop preventing shearing movement of the movable shearing member towards the fixed shearing member at all times except when the guiding means is displaced by the tension of the strip material.

2. In a machine for feeding strip material to work pieces, a frame, a shearing member mounted in normally fixed relationship to the frame with a cutting edge transverse to the direction of travel of the strip material fOr shearing the material into work-piece lengths, a second shearing member co-operating with the aforesaid shearing member to sever the material, a support for said second shearing member, means to displace said support and its shearing member automatically relatively to the first mentioned shearing member to effect a shearing operation, a freely suspended pivotally supported guide for the strip material displaceable about its pivot axis by the tension of the material so as to position the material between the two shearing mem bers ready for cutting when the material is under working tension, and an abutment adapted to act as a stop against the support for the second mentioned shearing member and fixed in relation to said guide so as to be displaceable with the guide by the tension of the strip material in such manner that during the working or normal tension of the strip material the said abutment is held by the tension of the material in a position which leaves the support with its shearing member free to operate, but in the event of the strip material becoming untensioned, is freed and acts as a stop against said support to prevent a shearing operation.

3. A machine according to claim 2 wherein said support for the second mentioned shearing member and the said guide are both mounted to swing fore and aft relatively to the direction of travel of the strip material, the said guide comprising a swinging frame having fixed relatively thereto adjacent its pivot axis said abutment and carrying at a position remote from said axis spaced parallel guide members between and across which the strip material is drawn so as to apply a lift to the frame, said frame having its pivot axis so related to said guide members and the shearing zone that upon working tension being applied to the strip material the frame is lifted about such axis by the tension of the material to move said abutment into the inoperative position, but upon release of said tension the frame moves by gravity into a position which locates the said abutment in the position to act as a stop for the support for said second mentioned shearing member.

i. A machine according to claim 3 wherein said frame carries a parallel pair of guide rods disposed transversely relatively to the direction of feed of the strip material, the frame being pivoted at a'position spaced from the guide rods and parallel with but spaced from the axis about which the said support swings, the pivoted ends of said frame and support having fixed relatively thereto co-operating abutments projecting towards each other, the guide rods being supported by said frame between the co-operating shearing members whereby the working tension in the strip material is transmitted via the guide rods to lift the frame to displace the abutment carried by the frame out of the path of the abutment carried by the said support, the arrangement being such that upon releasing the tension in the strip material the frame will fall into a position which locates the said two abutments in opposition to each other to prevent the shearing member carried by said support from moving into the shearing zone.

5. In a machine for feeding strip material to work-pieces, a pair of shearing members disposed transversely relative to the path of feed of the strip material to the work, guiding means for the strip material, a freely suspended oscillatable support carrying said guiding means, an oscillatable support for one of said shearing members, means to drive said latter support in one direction to carry its shearing member across the other shearing member to sever the strip material, said supports intersecting so that the shearing member carried by one or said supports when moving towards the other shearing member trails behind and pushes upwardly the guiding means carried by the other support, and a pair of abutments on said supports adjacent their axes of oscillation and so related positionally as to be normally held out of alignment by reason of the tensioned strip material acting as a support for the guiding means, but being brought into alignment upon the strip material losing its tension and allowing the guiding means to drop so that the abutments act as stops to prevent driving of the shearing member support to the strip cutting zone.

JOHN IRVING NASMITH.

REFERENCES CITED The following-references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,106,727 O'Brien et a1 Aug. 11, 1914 1,993,951 Ashe Mar. 12, 1935 

